I have run two marathons. The first was run in ideal conditions on a flat course and I ran a 19 second negative split. The second was run on a day when it was 61 degrees with literally 100% humidity at the gun. I ran an 80 second positive split and consider that to be one of the best races of my life. There were plenty of people with 20 and 30 minute positive splits that day. Plus, as the weather got warmer, I think there was nothing anyone could do but slow down a bit so I think that 80 second positive was about the best I could possibly have hoped for.

It is worth noting that Pfitzinger says that recreational runners will run their best marathon with a slight positive split. As I recall, he thinks most don't really know how to push the outside edge of their ability so they'll do better by banking a couple of minutes

Personally, I think the evidence is fairly clear that your best marathon will be an even split, and by "even" I'm talking less than a minute positive or negative.

Short term goal: 17:59 5K

Mid term goal: 2:54:59 marathon

Long term goal:To say I've been a runner half my life. (I started running at age 45).